Fig. 1. HSC/RUs in tissues of the developing mouse embryos (total number per tissue). (A) Distribution of HSC/RUs in AGM, YS and the circulation of day 11-13 embryos. (B) HSC/RUs in the fetal liver of day 11-13 embryos. Numbers of HSC/RUs in tissues were estimated using a limiting dilution method and presented as described in Materials and Methods. Numbers of recipient mice (RM) and dilutions (D) used were as follows. (A) 11 d.p.c.: (AGM) 27RM, 2D; (YS) 25RM, 3D; (circulation) 16RM, 3D; 12 d.p.c.: (AGM) 25RM, 7D; (YS) 56RM, 13D; (circulation) 43RM, 9D. (B) Liver (11 d.p.c.) 23RM, 2D; (12 d.p.c.) 37RM, 6D; (13 d.p.c.) 55RM, 12D.